Desktop: Linux improve desktop integration (#3003)

* Move consts to extra module

* Add desktop icons

* Add xdg desktop file

* Improve window attributes

* Make icon background white

desktop/src/main.rs

@@ -6,6 +6,8 @@ use graphite_editor::messages::prelude::Message;
 use tracing_subscriber::EnvFilter;
 use winit::event_loop::EventLoop;
 
+pub(crate) mod consts;
+
 mod cef;
 use cef::{Setup, WindowSize};